8 W 240 fs diode-pumped Yb:Y2O3 ceramic thin-rod femtosecond amplifier

Development of an ultrafast laser system based on a Yb-doped fiber and a Yb:YAG thin-rod for the preclinical study of pigmented lesions treatment using a Hartley guinea pig

In this research, we developed an ultrafast laser system based on a Yb-doped fiber oscillator and Yb:YAG thin-rod amplifier to investigate the efficacy of the laser for the treatment of pigmented lesions. The developed laser exhibited an output power of 22.7 W, center wavelength of 1030 nm, repetition rate of 495 kHz, pulse energy of 45.9 µJ, and pulse duration of 1.56 ps, respectively. For a compact and stable chirped pulse amplification system, a chirped fiber Bragg grating (CFBG) stretcher and a chirped volume Bragg grating (CVBG) compressor, both with fixed dispersion, were used. The dispersion of the total laser systems was precisely compensated by adjusting the length of the passive fiber and utilizing the self-phase modulation effect of the fiber amplifier. The developed ultrafast laser system was then applied in preclinical studies for the treatment of pigmented lesions in a guinea pig model. Three colored squares, each measuring approximately 15 × 15 mm, were treated by scanning a focused beam with varying laser fluences ranging from 0.5 to 2 J/cm2, using wavelengths of 515 nm and 1030 nm. The colorimeter measurements, which were performed 1-5 weeks after laser treatment, indicated that the laser was effective in reducing pigment, particularly black and blue pigments at higher fluences. This research represents the first trial of a preclinical study on pigmented lesions using an ultrafast laser system with a pulse duration below 10 ps, shorter than the stress relaxation time of 10 nm melanin granules. The results are meaningful as they offer valuable insights into the effectiveness of ultrafast laser therapy.

High average power amplification of femtosecond pulses based on the Yb:CaYAlO4 crystal

In this paper, we demonstrated the direct amplification of femtosecond pulses with the Yb:CaYAlO₄ crystal for the first time. A compact and simple two-stage amplifier delivered amplified pulses with the average powers of 55.4 W for σ-polarization and 39.4 W for π-polarization at the center wavelengthes of 1032 nm and 1030 nm, corresponding to 28.3% and 16.3% optical-to-optical efficiencies, respectively. These are to the best of our knowledge the highest value achieved with a Yb:CaYAlO₄ amplifier. Upon using a compressor consisting of prisms and GTI mirrors, a pulse duration of 166-fs was measured. Thanks to the good thermal management, the beam quality (M²) parameters <1.3 along each axis were maintained in each stage.